Cellular immune response to falciparum malaria is being studied in West Africa with respect to immunosuppressor and specific T-cell response to malaria antigen. Mitogenicity of P. falciparum is being investigated. The role of the spleen in experimental malaria is being studied in rhesus monkeys and in mice in relation to monocyte kinetics during infection. Studies in the susceptibility of various strains of mice to P. berghei will be conducted with respect to the genetic control of the immune response in malaria.